So in this case zuluedm.com email has been set up to be sent from Google Mail. Your MX records could be anything, it doesn't matter. So the issue is when sending mail from our platform we need to tell the Internet that this is not SPAM and the email coming from our platform is legitimate.

How do you do this?

Simple. Go to your DNS management software (ask your tech support person if you have one) and add in a Text (TXT) lined with the following and don't forget to add the quotes "":